A frequency response approach to autotuning of multivariable controllers

The relay auto-tuning technique for PID controllers is here extended to tune multivariable controllers. In the case of significant interaction, a fully cross-coupled multivariable controller rather than a decentralized controller should be employed. In this paper, an autotuning method for multivariable controllers from sequential relay feedback is proposed. The frequency response a m × m multivariable process is identified from limit cycles using a FFT-based method, and a multivariable controller is computed with linear least squares frequency response fitting. Various typical examples are included for illustration of the effectiveness of the method.